This disclosure relates, in various exemplary embodiments, to polycarbonate compositions and articles formed from such compositions having minimum halogen content and improved fire-retardance and/or drip-resistant characteristics, as well as uses thereof. For example, the disclosure relates to glass fiber reinforced polycarbonate based resin compositions having robust thin-wall fire-retardance, acceptable impact resistance, and good manufacturing and processing characteristics.
With their strength and clarity, polycarbonate (PC) and copolycarbonate resins offer many significant advantages and are utilized for a number of different commercial applications. Polycarbonate materials are playing a vital role today in applications including electronic engineering (“E&E”) parts, mechanical parts and so on. Unfortunately, polycarbonate resins are inherently flammable and can drip hot molten material causing nearby materials to catch fire as well. Thus, in order to safely utilize polycarbonates in many applications, it is necessary to include additives which retard the flammability of the material and/or which reduce dripping.
A variety of different materials have been described for use in producing fire-retardant (FR) and/or drip-resistant polycarbonates. Exemplary of these are the materials described in U.S. Pat. Nos. 3,971,756; 4,028,297; 4,110,299; 4,130,530; 4,303,575; 4,335,038; 4,552,911; 4,916,194; 5,218,027; and, 5,508,323.
Fire-retardance additives applied today typically include various sulfonate salts, phosphorus acid esters, brominated and/or chlorinated flame retardants, etc. Moreover, the phosphate additives, which are used at relatively high loadings (>5% and around 10% to produce similar V0 performance) will deteriorate overall material mechanical performance. Furthermore, brominated and chlorinated additives, and even some fluorinated additives at certain loadings are prohibited by various NGO's and environmental protection rules, such as Blue Angle, TCO'99, DIN/VDE, etc. Consequently, sulfonate salts have become fairly widely used in the industry to produce fire-retardant polycarbonate materials.
Examples of such sulfonate salts are perfluoroalkane sulfonates, such as potassium perfluorobutane sulfonate (“KPFBS”, also known as “Rimar salt”) and potassium diphenylsulfone sulfonate (“KSS”). For example, the use of perfluoroalkane sulfonates in polycarbonate resins is described in U.S. Pat. No. 3,775,367. Also, U.S. Pat. No. 6,353,046 discloses that improved fire properties can be imparted to polycarbonate resin compositions by incorporating into the polycarbonate, potassium perfluorobutane sulfonate, and a cyclic siloxane, such as octaphenylcyclotetrasiloxane.
For KSS, only limited fire-retardance performance can be obtained when it is used alone. The conventional means for enhancing the fire-retardant properties while retaining transparency has been the incorporation of soluble organic halogen additives with KSS. For example, commercial grades of LEXAN® (General Electric Co.) polycarbonate resins (e.g. 940A, 920A) contain a combination of KSS (0.3 phr) and a tetrabromo-bisphenol/bisphenol A copolymer (0.5 phr, net 0.13 phr bromine content). Without the bromine, the 920A and 940A grades have inconsistent/unreliable performance in the UL94 VO 125 mil flammability test that these grades are designed to meet.
On the other hand, environmental concerns and guidelines directed to these issues are of particular importance today. Such regulations and guidelines include Blue-Angel, TCO99, and DIN/VDE. For example, current “eco-FR” LEXAN®, which is mostly loaded with Rimar salt at a level of 0.05-0.08%, is not Blue Angel conforming because of the fluorine content. Moreover, Rimar can generate bubbles that cause haze under higher processing temperatures. The brominated additive used in conjunction with KSS is not suitable for consumer products which are subject to “ECOs-friendly” standards, since these standards prohibit the inclusion of bromine or chlorine based fire-retardance additives.
Additionally, it is known that glass fiber reinforced polycarbonates have been widely used for their good combination of mechanical properties and heat resistance, and grades of such polycarbonates with fire retardance are playing a vital role today in various applications including E&E parts, mechanical structure parts and so on. Use of these resins has been increasing rapidly in recent years with related industrial development. Moreover, there are increasing market needs for new formulations with high FR ratings, and thinner gages.
An issue with manufacturing such glass fiber reinforced polycarbonate compositions is, however, that they do not have robust fire retardance performance, particularly with the inclusion of rigid particles, such as titanium oxide.
There accordingly remains a need in the art for the production of polycarbonate compositions with certain amounts of glass fiber that can readily produce an article of manufacture with minimum content of halogen, such as bromine and chlorine. These compositions also need to exhibit good fire-retardancy and drip-resistance, in a cost-effective manner, have thinner gages, and good manufacturability characteristics, among others.